Recently I’ve set up a file server for both Windows and Linux. When I went to mount the file system on Linux, things were broken – because I hadn’t paid attention to user ID and group ID when I created users on my different Unix machines.

So I needed to change the UID and GID of a user, then update the files. Luckily, someone had already done the work:

One wrinkle that I wasn’t expecting: you can’t change the user ID of a user who has a running process. So I had to create a second user with adduser, add that user as in /etc/groups for sudo, log in as that user, and then change the user ID of the original user.

When I ran this on Ubuntu and Raspbian, I saw about 4 errors in /proc which I ignored. There’s probably a faster way to do to this using xargs rather than running -exec each time, but I was a little worried I might exceed what I could pass in on a command line (I had hundreds of thousands of files) so I let it do its thing.

Like the rest of the world, I wanted to have a static IP for a Raspberry Pi that was on a wifi network. Like the rest of the world, I couldn’t figure out how to do it after three attempts. At that point, like the rest of the world I gave up and decided to make my DHCP server do the work instead of the Pi.

Here’s how I did it:

1. On the Pi, edit /etc/wpa_supplicant.conf and add:

network={
ssid="My_SSID"
psk="My_wifi_password"
}

2. Reboot and get an IP address through DHCP.

3. Confirm that I can see the world with the DHCP address.

4. ifconfig wlan0 and copy down the hardware Ethernet address for wlan0 (let’s pretend it was 00:11:22:33:44:56).